Seismic data is acquired to investigate and map the structures and character of geological formations under the earth. Seismic data is typically gathered by laying out seismic receivers (e.g., geophones or similar sensors) in a survey area and directing one or more seismic sources such as vibrator trucks to move from shot point to shot point and direct seismic energy into the ground. As the seismic sources direct seismic energy into the earth where they are reflected and/or refracted by interfaces between subsurface geological formations the seismic receivers sense the resulting reflected and/or refracted energy, thereby acquiring seismic data that provides information about the geological formations under the ground. Basically a seismic source emits a wavefield that propagates down through the earth and is reflected and/or refracted by interfaces between subsurface geological formations then propagates back to the surface where the receivers detect and discretely sample the returning, ascending or upcoming wavefield.
Typically, thousands of discrete seismic receivers are used to gather seismic data. The seismic receivers are generally laid out in lines that are substantially parallel and laterally spaced at equal distances and uniformly spaced down the line. In this configuration, uniform coverage of the subsurface is achieved. It is conventional that receiver spacing along the lines is closer than the spacing between the lines and that, therefore, the wavefield detected by the sensors is less well sampled in the lateral direction (perpendicular to the receiver lines) in most seismic surveys. The normal ratio of the station spacing to the line spacing runs between 2 and 30 to 1. This means that the spacing of the receivers along the line is between half and one thirtieth the spacing between parallel receiver lines. This is normally due to the costs and expense of adding additional receiver lines that can dramatically increase the expense of the survey to achieve a better sampling of the returning, ascending or upcoming wavefield.